Question

How can I concatenate a specific attribute of all elements together using SQL XQuery?

I have a table like this:

InvoiceId   Details
---------   -----------------------------------------------------------------
1001        <Stuff Id="101" p="3" q="5"/><Stuff Id="102" q="4"/><Stuff Id="103"/>
1002        <Stuff Id="201" /><Stuff Id="202" q="2"/>

and need this result =>

InvoiceId  IdDetails
---------   ---------------------
1001        101,102,103
1002        201,202

Answer 1

declare @T table(InvoiceId int, Details xml)
insert into @T
select 1001, '<Stuff Id="101" p="3" q="5"/><Stuff Id="102" q="4"/><Stuff Id="103"/>' union all
select 1002, '<Stuff Id="201"/><Stuff Id="202" q="2"/>'

select InvoiceId,
       stuff((select ','+t.n.value('@Id', 'varchar(10)')
              from Details.nodes('Stuff') as t(n) 
              for xml path('')), 1, 1, '') as IdDetails  
from @T

Only unique values for Id.

select InvoiceId,
       stuff((select ','+s.id
              from Details.nodes('Stuff') as t(n)
                cross apply (select t.n.value('@Id', 'varchar(10)')) as s(id) 
              group by s.id
              for xml path('')), 1, 1, '') as IdDetails  
from @T